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White Light Nanoparticles

In the burgeoning field of nanotechnology, all kinds of strange and miraculous effects are made possible by breaking elements into particles and either using their innate particular properties or manipulating them until they exhibit the desired characteristics. White light nanoparticles are another amazing discovery in Nanotechnology.

One of the most effective recent experiments using this principle involves silver nanoparticles, which researchers at the University of Utah have organized into a microscopic white light-emitting mirror that has a wide range of useful applications in the future of the medical industry.

Apparently this nano-mirror works in tandem with a microscope to reveal not only the outer but also the inner microscopic structure of a specimen. The only requirements for the specimen: it needs to be nearly opaque as well as a biological substance. So far, some of the key elements on which this new technique has been tested include the iridescent scales of the photonic beetle, malignant tumor cells, and other key body materials such as bone.

The leader of this new study is John Lupton, an associate professor at the U of U who says that since carbon is a semi-biological substance, this technique may also be applicable in areas like the airplane industry. Plastics built of carbon-fibers are the latest material being used in constructing aircraft tails, wings, and fuselages.

The silver nanoparticle mirror combined with a microscope offers a unique opportunity to test these aircraft parts for fatigue related to stress and decay that build up over time from natural wear and tear. By anticipating this fatigue ahead of time, the aircraft industry might be able to replace parts and save lives.

Microscopes in general have always used white light, and their basic function has changed very little since their invention in the 17th century. But if a specimen does not naturally have enough contrast or detail, it can be difficult to get an accurate close-up view. This is because the microscope passes white light through its subjects in order to provide the clear, accurate picture that they have become famous for.

Before nanotechnology stepped in, the most significant upgrade this machine had undergone was limited to the invention of electron microscopes. They are powerful enough to provide a detailed close-up of even the tiniest structures, yet at the same time they are too expensive to be widely used. This means that they are not always readily available for researchers and scientists. And, as Lupton points out, their effectiveness is limited; they cannot be used universally on every type of sample.

These problems were the main motivator for the Utah team. Before their efforts, others had tried to enhance or revise the microscope’s abilities by using a fairly common practice known as laser microscopy or sometimes fluorescence microscopy.

In this technique, scientists make the microscope specimen emit light by using a laser on it. In some cases the specimen naturally reacts with the laser in this way; in others, it becomes necessary to inject or “label” the specimen with a dose of fluorescent dye which the laser then activates. The main difficulty with this process arises when a researcher is dealing with a specimen that cannot naturally be laser-lit and yet doesn’t respond well to the fluorescent dyes—since it turns out that when activated by the laser, such dyes produce toxic chemicals that almost categorically kill any living cells they come into contact with.

Having taken all of these issues into account, Lupton and his team realized that engineering nanoparticles might solve everything. They avoid using fluorescent labels completely. Rather, they have created a cluster of nanoparticles that naturally emits white light, which they then place under the specimen in order to provide white light from both sides and enhance researchers’ ability to see clearly.

They also adjusted the technique so that instead of a conventional laser, they use infrared. This type of light wavelength seems to interact better with the silver nanoparticles that they chose to use, says Lupton. When excited or activated by the laser, these silver particles form “plasmonic hotspots,” which collect and gather the resultant white light into concentrated areas and then shoot them up through the specimen, working in tandem with the microscope’s white light on the other side.

The white light transmitted by these super-emitting white light nanoparticles can then be broken into a spectrum which reveals detailed and useful information about the specimen’s structure and composition. In other words, examining something up close has never been easier.

The University of Utah team, led by Lupton, wanted to solve these problems in order to address a potentially lucrative opportunity. Scientists have been trying to build an ideal photon crystal that could be used to manipulate light waves in the visible spectrum—they believe that if they could do this, they could transform the technology into ultrafast optical computing systems that run entirely on visible light as opposed to electricity. Without the photon crystal structure, this dream is impossible. With it, you have the next generation of computers, machines that make our computers look as old-fashioned as typewriters do now.

The difficulty lay in developing this photon crystal properly, and scientists were simply at a dead end…until they found a Brazilian beetle whose semi-opaque green shell appears to exhibit the exact characteristics they were looking for. Dubbed the “photonic beetle,” the outer layer of this insect’s wing case has a perfect photon crystalline structure. Scientists were ecstatic and wanted to study their discovery further—but hit a wall when their conventional microscopes proved insufficient for the task. Visible light scatters when it hits the shell’s scales, thwarting the essential task of viewing their inner structure.

That’s where Lupton and his team stepped in. To this date, they have developed a mirror built of microscopic silver nanoparticles that react very strongly with infrared laser to illuminate the beetle scales for research. Researchers have also successfully used the new microscopy technology to view the intimate details of tumor cells, human bone samples and other important amorphous materials. Such a breakthrough, with its implications for medicine and technology, could drastically affect the way we function in the future.